broadFileSystemAccess UWP

This capability is not listed in the "designer" of Package.appxmanifest, you have to add it manually via code.

Go to Solution Explorer and right-click Package.appxmanifest. Select View Code.

In the code view update the Package element to contain the following:

<Package
  ...
  xmlns:rescap="http://schemas.microsoft.com/appx/manifest/foundation/windows10/restrictedcapabilities"
  IgnorableNamespaces="uap mp rescap">

Do not duplicate the IgnorableNamespaces attribute, just append rescap to the end of its value. Now scroll down below and find <Capabilities>. Inside add the broadFileSystemAccess capability as follows:

<rescap:Capability Name="broadFileSystemAccess" />